Active acoustic and vibration noise canceling in waterproof camera

ABSTRACT

A camera includes one or more microphone pairs. A first microphone (e.g., a main microphone) is ported to the outside of the camera and captures the desired external audio signal, but may also capture undesired vibrational noise. A second microphone has a similar structure to the first microphone, but is not ported to the outside of the camera. Instead, the second microphone is ported into an enclosed cavity (e.g., 1-2 cubic centimeters in volume). The second microphone may pick up the same vibration excitation and internal acoustic noise as the first microphone but very little of the desired external acoustic sounds around the camera. The unwanted noise can then be removed by subtracting the second audio signal from the second microphone from the main audio signal from the main microphone.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/405,047 filed on Oct. 6, 2016 which is incorporated by referenceherein.

BACKGROUND Field of Art

The disclosure generally relates to audio systems and in particular tocanceling vibration noise in a camera.

Description of Art

In a waterproof camera, a protective membrane may be placed in front ofthe microphone to prevent water from entering the camera. When thecamera moves or external forces are applied to the camera, the membranemay vibrate. The vibrations may be picked up as acoustic noise by themicrophone. Additionally, other vibrating components inside the cameramay generate additional noise that may reach the microphone. This noiseis generally undesirable and may reduce the quality of desired audiosignal.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed embodiments have advantages and features which will bemore readily apparent from the detailed description, the appendedclaims, and the accompanying figures (or drawings). A brief introductionof the figures is below.

FIG. 1 is a block diagram illustrating an example embodiment of an audiosub-system of a camera.

FIG. 2 is an example embodiment of a camera.

FIG. 3 is a flowchart illustrating an example process for processing anaudio signal in a camera.

DETAILED DESCRIPTION

The figures and the following description relate to preferredembodiments by way of illustration only. It should be noted that fromthe following discussion, alternative embodiments of the structures andmethods disclosed herein will be readily recognized as viablealternatives that may be employed without departing from the principlesof what is claimed.

Reference will now be made in detail to several embodiments, examples ofwhich are illustrated in the accompanying figures. It is noted thatwherever practicable similar or like reference numbers may be used inthe figures and may indicate similar or like functionality. The figuresdepict embodiments of the disclosed system (or method) for purposes ofillustration only. One skilled in the art will readily recognize fromthe following description that alternative embodiments of the structuresand methods illustrated herein may be employed without departing fromthe principles described herein.

CONFIGURATION OVERVIEW

In an embodiment, a camera includes one or more microphone pairs. Afirst microphone (e.g., a main microphone) is ported to the outside ofthe camera and captures the desired external audio signal, but may alsocapture undesired vibrational noise. A second microphone has a similarstructure to the first microphone, but is not ported to the outside ofthe camera. Instead, the second microphone is ported into an enclosedcavity (e.g., 1-2 cubic centimeters in volume). The second microphonemay pick up the same vibration excitation and internal acoustic noise asthe first microphone but very little of the desired external acousticsounds around the camera. The unwanted noise can then be removed bysubtracting the second audio signal from the second microphone from themain audio signal from the main microphone.

In a particular embodiment, a camera or other audio capture deviceincludes an audio sub-system that includes structures for enabling noisecancellation. A housing has a microphone port comprising an opening. Afirst waterproof membrane spans the opening. A printed circuit board iscoupled to an interior surface of the housing below the microphone port.The printed circuit board comprises a main microphone opening under themicrophone port and a reference microphone opening laterally offset fromthe microphone port. A main microphone is mounted to a bottom surface ofthe printed circuit board below the main microphone opening. The mainmicrophone detects ambient audio and generates a main audio signal. Areference microphone is mounted to a top surface of the printed circuitboard above the reference microphone opening. The reference microphonecaptures a reference audio signal. A second waterproof membrane spansthe reference microphone opening. A reference structure is configuredsuch that a reference cavity exists below the second waterproofmembrane. One or more sealing gaskets isolates the second microphonefrom the microphone port. A processor (e.g., by subtracting thereference audio signal from the main audio signal).

Audio Sub-System Architecture

FIG. 1 illustrates a cross-sectional view of an embodiment of an audiosub-system 102 of a camera 100. The camera 100 comprises a housing 110with an opening 114 (e.g., a main microphone port) in a top surface ofthe housing 110 sealed by a waterproof membrane 112. The waterproofmembrane 112 covers a main microphone (Mic 1) 116 that is mounted to abottom surface of an audio printed circuit board (PCB) 118 on anopposite side of the audio PCB 118 from the member 112. The waterproofmembrane 112 prevents water from reaching the main microphone 116 butenables acoustic waves to reach the main microphone 116 so that the mainmicrophone 116 can capture the ambient audio without substantialdistortion. The audio PCB 118 may include additional electronicssupporting the audio sub-system 102 such as an audio processor, memory,storage, and interconnections between the components. The audio PCB 118may include an opening aligned with the opening 114 in the housing 110to enable ambient audio to reach the main microphone 116. In anembodiment, the audio PCB 118 and the attached main microphone 116 areattached to the housing 110 via an elastomer and sealant. A firstacoustical cavity (V1) 120 is formed between the main microphone 116 andthe membrane 112.

A reference microphone (Mic 2) 122 is mounted at a different position onthe audio PCB 118. For example, the reference microphone 122 may bemounted on a top surface of the audio PCB 118 (e.g., on the side facingthe membrane 112) and may also be coupled to an interior surface of thehousing 110. The bottom surface of the audio PCB 118 below the referencemicrophone 122 may attach to a reference structure 124 cantilevered froman interior side surface (e.g., perpendicular to the top surface) of thehousing 110. The reference structure 124 may include a waterproofmembrane 126 below an opening of the PCB audio 118 below the secondmicrophone 122. The waterproof membrane 126 may be substantially similarin material and thickness to the waterproof membrane 112 such that itproduces a similar or vibrational response in response to the same inputstimulus.

In an embodiment, the reference structure 124 is attached to the bottomsurface of the audio PCB 118 via an elastomer and sealant each havingsimilar structural and material characteristics to the elastomer andsealant used to attach the main microphone 116 to the housing 110. Asecond acoustical cavity (V2) 128 is formed between the referencemicrophone 122 and the second membrane 126. This second acousticalcavity 128 may have substantially the same characteristics as the firstacoustical cavity 120 (e.g., similar shape, volume, and acousticcharacteristics). A reference cavity 130 having a volume V3 is alsoformed below the membrane 126 and above the cantilever referencestructure 124. The volume V3 may be dampened by a dampening element 132.

FIG. 1 also illustrates sealing gaskets 134 between the top surface ofthe PCB 118 and the interior surface of the housing 110 on either sideof the opening 114 in order to isolate the first acoustical cavity 120.Similar gaskets 136 may be placed on the sides of the second acousticalcavity 128 to similarly isolate the second acoustical cavity 128. Thegaskets 134, 126 may comprise ring-shaped gaskets with openings thatalign with the main microphone opening and the reference microphoneopening respectively in the PCB 118. The gaskets 134, 126 substantiallyisolate the reference microphone from the opening 114. Furthermore, thegaskets 134, 126 substantially acoustically isolate the first acousticalcavity and the second acoustical cavity.

FIG. 1 further illustrates a main PCB 150. The main PCB 150 may includevarious electronic components that support general functionality suchas, for example, an image sensor, video processor, memory controller, orother supporting components. The main PCB 150 may include variouscomponents 138 (e.g., integrated circuits or other surface mountcomponents) that may generate vibrational forces resulting invibrational noise inside the housing 110. These vibrations may occur inresponse to external forces F₁ acting on the housing 110 caused by, forexample, a user handling the camera, a mount attached to the camera thatexerts a force on the camera in response to motion, or other externalforces.

As can be seen from FIG. 1, the reference microphone 122 is isolatedfrom the external audio source that will be captured by the mainmicrophone 116. However, the reference microphone 122 and the mainmicrophone 116 will both pick up similar vibrational noise because therespective microphone 116, 122, acoustical cavities 120, 128, andmembranes 112, 126 are similar positioned and structured. Furthermore,both microphones 116, 122 are affixed to the same PCB 118 and thereforepick up similar vibrations from the PCB 118. The reference cavity 130and the dampening element 132 within it may also be structured in amanner that causes the reference microphone 122 to capture similarvibrational noise (e.g., frequency and amplitude as the main microphone116. Alternatively, the structure of the reference cavity 130 anddampening element 132 can characterize a baseline noise that can enablea signal processor to estimate the vibrational noise that will becaptured by the main microphone 116. The audio signal from the referencemicrophone 122 (or a transformation thereof) can be subtracted from themain audio signal from the main microphone 116 to improve thesignal-to-noise ratio of the audio signal.

FIG. 2 illustrate an embodiment of an example camera 200 that mayinclude the audio sub-system 102. The camera 200 may comprise a housing110 having a camera lens 204 structured on a front surface of thehousing, various indicators on the front of the surface of the housing202 (such as LEDs, a display 206, and the like), various inputmechanisms (such as buttons, switches, and touch-screen mechanisms), andelectronics (e.g., imaging electronics, power electronics, etc.)internal to the housing 202 for capturing images via the camera lensand/or performing other functions. The camera 200 may be configured tocapture images and video, and to store captured images and video forsubsequent display or playback.

The camera 200 can include various indicators, including a display panel206. The camera 200 can also include buttons 210 configured to allow auser of the camera to interact with the camera, to turn the camera on,and to otherwise configure the operating mode of the camera. The camera200 can also include one or more audio sub-systems 102 which may eachhave the structure described above.

FIG. 3 is a flowchart illustrating an example embodiment of a processfor processing an audio signal. A main audio signal captured by the mainmicrophone is received 302 by a processor. A reference audio signalcaptured by the reference microphone is also received 304 at theprocessor. An output audio signal is generated 306 based on the mainaudio signal and the reference audio signal that has reduced vibrationalnoise relative to the main audio signal. For example, the output audiosignal may be generated by subtracting the reference audio signal fromthe main audio signal. Alternatively, a predefined transformation may beapplied to the reference audio signal to generate a transformedreferenced audio signal, and the output audio signal is then generatedby subtracting the transformed referenced audio signal from the mainaudio signal. Here, the transformation may be predetermined based on acharacterization of the noise captured by the reference audio signalrelative to the main audio signal, which may relate to the physicalproperties of the reference cavity 130 and dampening element 132.

In an alternative embodiment, the audio sub-system 102 of FIG. 1, may beintegrated into an audio capture device that is not necessarily acamera. Here, the various components discussed in FIG. 1 may beintegrated with a device housing of the audio capture device in the samemanner that they are integrated into the housing described above.

ADDITIONAL CONFIGURATION CONSIDERATIONS

Throughout this specification, some embodiments have used the expression“coupled” along with its derivatives. The term “coupled” as used hereinis not necessarily limited to two or more elements being in directphysical or electrical contact. Rather, the term “coupled” may alsoencompass two or more elements are not in direct contact with eachother, but yet still co-operate or interact with each other, or arestructured to provide a drainage path between the elements.

Likewise, as used herein, the terms “comprises,” “comprising,”“includes,” “including,” “has,” “having” or any other variation thereof,are intended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus.

In addition, use of the “a” or “an” are employed to describe elementsand components of the embodiments herein. This is done merely forconvenience and to give a general sense of the invention. Thisdescription should be read to include one or at least one and thesingular also includes the plural unless it is obvious that it is meantotherwise.

Finally, as used herein any reference to “one embodiment” or “anembodiment” means that a particular element, feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. The appearances of the phrase “in oneembodiment” in various places in the specification are not necessarilyall referring to the same embodiment.

Upon reading this disclosure, those of skill in the art will appreciatestill additional alternative structural and functional designs asdisclosed from the principles herein. Thus, while particular embodimentsand applications have been illustrated and described, it is to beunderstood that the disclosed embodiments are not limited to the preciseconstruction and components disclosed herein. Various modifications,changes and variations, which will be apparent to those skilled in theart, may be made in the arrangement, operation and details of the methodand apparatus disclosed herein without departing from the spirit andscope defined in the appended claims.

The invention claimed is:
 1. A camera comprising: a housing having amicrophone port comprising an opening in the housing; a first waterproofmembrane spanning the opening in the housing; a printed circuit boardcoupled to an interior surface of the housing below the microphone port,the printed circuit board comprising a main microphone opening under themicrophone port and a reference microphone opening laterally offset fromthe microphone port; a main microphone mounted to a bottom surface ofthe printed circuit board below the main microphone opening, the mainmicrophone for detecting ambient audio and generating a main audiosignal; a reference microphone mounted to a top surface of the printedcircuit board above the reference microphone opening, the referencemicrophone to capture a reference audio signal; a second waterproofmembrane spanning the reference microphone opening; a referencestructure configured such that a reference cavity exists below thesecond waterproof membrane; one or more sealing gaskets to isolate thesecond microphone from the microphone port; and a processor to generatean output audio signal based on the main audio signal and the referenceaudio signal.
 2. The camera of claim 1, wherein the reference structurecomprises: a dampening element below the reference cavity to dampenvibrations experienced by the reference structure.
 3. The camera ofclaim 1, wherein the one or more sealing gaskets comprise: a firstgasket between an interior surface of the housing and a top surface ofthe printed circuit board, the first gasket having an opening alignedwith the main microphone opening; and a second gasket between a bottomsurface of the printed circuit board and a tope top surface of thereference structure, the second gasket having an opening aligned withthe reference microphone opening.
 4. The camera of claim 3, wherein afirst acoustical cavity exists in the opening of the first gasket abovethe main microphone, below the first waterproof membrane, and wherein asecond acoustical cavity exists in the opening of the second gasketbelow the reference microphone, above the second waterproof membrane. 5.The camera of claim 4, wherein the first acoustical cavity and thesecond acoustical cavity exhibit a substantially same acousticalresponse to vibrations.
 6. The camera of claim 4, wherein the firstacoustical cavity and the second acoustical cavity have approximately asame volume.
 7. The camera of claim 1, wherein the reference structurecomprises: a cantilever structure coupled to an interior side face ofthe housing perpendicular to a top face including the microphone port.8. The camera of claim 1, wherein the processor is configured togenerate the output audio signal by subtracting the reference audiosignal from the main audio signal.
 9. The camera of claim 1, wherein theprocessor is configured to generate the output audio signal by applyinga transformation to the reference audio signal to generate a transformedreference audio signal and subtracting the transformed reference audiosignal from the main audio signal.
 10. An audio device comprising: adevice body having a microphone port comprising an opening in the devicebody; a first waterproof membrane spanning the opening in the devicebody; a printed circuit board coupled to an interior surface of thedevice body below the microphone port, the printed circuit boardcomprising a main microphone opening under the microphone port and areference microphone opening laterally offset from the microphone port;a main microphone mounted to a bottom surface of the printed circuitboard below the main microphone opening, the main microphone fordetecting ambient audio and generating a main audio signal; a referencemicrophone mounted to a top surface of the printed circuit board abovethe reference microphone opening, the reference microphone to capture areference audio signal; a second waterproof membrane spanning thereference microphone opening; a reference structure configured such thata reference cavity exists below the second waterproof membrane; one ormore sealing gaskets to isolate the second microphone from themicrophone port; and a processor to generate an output audio signalbased on the main audio signal and the reference audio signal.
 11. Theaudio device of claim 10, wherein the reference structure comprises: adampening element below the reference cavity to dampen vibrationsexperienced by the reference structure.
 12. The audio device of claim10, wherein the one or more sealing gaskets comprise: a first gasketbetween an interior surface of the device body and a top surface of theprinted circuit board, the first gasket having an opening aligned withthe main microphone opening; and a second gasket between a bottomsurface of the printed circuit board and a top surface of the referencestructure, the second gasket having an opening aligned with thereference microphone opening.
 13. The audio device of claim 12, whereina first acoustical cavity exists in the opening of the first gasketabove the main microphone, below the first waterproof membrane, andwherein a second acoustical cavity exists in the opening of the secondgasket below the reference microphone, above the second waterproofmembrane.
 14. The audio device of claim 13, wherein the first acousticalcavity and the second acoustical cavity exhibit a substantially sameacoustical response to vibrations.
 15. The audio device of claim 13,wherein the first acoustical cavity and the second acoustical cavityhave approximately a same volume.
 16. The audio device of claim 10,wherein the reference structure comprises: a cantilever structurecoupled to an interior side face of the housing perpendicular to a topface including the microphone port.
 17. The audio device of claim 10,wherein the processor is configured to generate the output audio signalby subtracting the reference audio signal from the main audio signal.18. The audio device of claim 10, wherein the processor is configured togenerate the output audio signal by applying a transformation to thereference audio signal to generate a transformed reference audio signaland subtracting the transformed reference audio signal from the mainaudio signal.
 19. A camera comprising: a housing having a microphoneport comprising an opening in the housing; a printed circuit board; amain microphone to detect a main audio signal based on ambient audioentering the microphone port and vibration noise generated by componentsof the camera, the main microphone mounted to a first surface of theprinted circuit board; a first waterproof membrane spanning a firstacoustical cavity adjacent to the main microphone; a referencemicrophone substantially acoustically isolated from the microphone port,the reference microphone capturing a reference audio signal based on thevibration noise generated by the components of the camera, the referencemicrophone mounted to a second surface of the printed circuit board; asecond waterproof membrane spanning a second acoustical cavity adjacentto the reference microphone; one or more sealing gaskets to isolate thesecond acoustical cavity from the first acoustical cavity; and aprocessor to generate an output audio signal based on the main audiosignal and the reference audio signal.